Group-directed communications are commonplace in enterprise and public safety communication systems. With regard to audio communications, one end device (transmitter) transmits an audio signal (i.e., a “talkburst”) to a given group (i.e. a “talkgroup”) of receiving end devices (receivers). These receivers reproduce the audio signal through an amplified speaker. The manner in which the receivers operate usually results in the reproduced sound being audible to people other than merely the intended recipient.
Typically, in these group communication systems, the end devices are located near each other. This is particularly true in public safety uses, in which personnel often respond to incidences in a group, and this group (or a subset thereof) is located in the same local area for an extended period of time. If a transmitter and receiver are collocated, the microphone on the transmitter may pick up the audio signal that has been transmitted by the transmitter and reproduced by a loudspeaker on the receiver. Under certain conditions, the resulting feedback loop can reinforce itself to create an undesirable acoustic signal, herein referred to as “howling.”
As above, such situations are especially prevalent in public safety incidents in which the transmitter and receiver(s) are often disposed within sufficient range and for a long enough time period to cause howling. While howling is irritating in normal situations, it is potentially disastrous during public safety incidents, notably if critical information is lost, misconstrued due to the feedback, or must be re-transmitted causing an unacceptable delay. It is therefore desirable to reduce, if not eliminate, instances of howling.